Method of and apparatus for generating signals

ABSTRACT

A method of and apparatus for generating in a power supply system a transmission signal with a frequency bearing a fixed relationship to the mains frequency of the power supply system. An impulse sequence whose repetition frequency bears the aforementioned fixed relationship to the mains frequency is formed by frequency multiplication and frequency division. A tank circuit connected to the power supply system and tuned at least approximately to the said repetition frequency is excited by it into oscillation in each cycle of the impulse sequence.

United States Kucera Dec. 11, 1973 [54] METHOD OF AND APPARATUS FOR 2,772,359 11/1956 Modiano 307/273 X GENERATING SIGNALS 2,852,671 9/1958 Cohen 328/38 X 3,343,094 9/1967 Kocher 328/25 X Inventor: Jaromlr Kucera, g 3,349,184 10/1967 Morgan... 328/16 x Switzerland 3,439,278 4/1969 vFarrow.... 328/25 X [73] Assigneez ze g U Switzerland 3,617,902 ll/l97l Bauer 328/38 [22] i dl J1 1972 Primary ExaminerJohn S. Heyman [21] pp No; 259 199 Attorney-Werner W. Kleeman [30] Foreign Application Priority Data [57] ABSTRACT Jul 1 I971 Switzerland 8913, A method of and apparatus for generating in a power y supply system a transmission signal with a frequency [52] CL 328/223 328/38 328/39 bearing a fixed relationship to the mains frequency of [51] Int. Cl. 6 3/02 the power supply system. An impulse sequence whose [58] Field 16 21 22 repetition frequency bears the aforementioned fixed 39 5 2 relationship to the mains frequency is formed by frequency multiplication and frequency division. A tank [56] References Cited circuit connected to the power supply system and UNITED STATES PATENTS tuned at least approximately to the said repetition fre- 3 182 265 5/ 965 w 328,223 X quency is excited by it into oscillation in each cycle of l u th l 3,446,947 5/1969 Overstreet 328/39 X e Imp Se sequence 3,721,904 3/1973 Verhoeven 328/39 10 Claims, 5 Drawing Figures u H 1 10 P 4 ffl i 16 19% 2% l %4 1 U 1 I l l i ,r- I i N 3 50. I 24 i 3 12 13 35 31 33 25 FREQ 23 mm Div/06R Mum PUEk 21 18 5 6 14 34 32 22 i 29 i PHENTED DEC! 1 I975 SHEET 1 BF 5 PATENTEUBEBI 1 1975 saw 3 or 5 PATENTEUUEBI 1 1% I 5.718.723

sumu'urs U221 Q *I- lllllllll o v t U251 I b,

METHOD OF AND APPARATUS FOR GENERATING SIGNALS BACKGROUND OF THE INVENTION The present invention relates to a new and improved method of and apparatus for generating signals, and this invention also relates to application of this method of the transmission of information.

It is known that power or current supply networks can be also used for transmitting signals. Thus, in the ripple control art, for example, alternating current impulses, preferably of audio frequency, delivered by a transmitter are superimposed upon a power supply system at a central location by means of coupling elements. These alternating current impulses disseminate throughout the power supply system and, as required, can be removed therefrom at any point with known means and evaluated for example for remote-control purposes. In ripple control, the required direction of propagation of the aforementioned signals coincides with the direction of energy flow in the power supply system.

It has also been proposed to use the power supply system for transmitting signals in the opposite direction to energy flow. Whereas in the first case of ripple control it is standard practice to use only one central transmitter and a large number of receivers, the second case is concerned in particular with the transmission of signals by means of a plurality of transmitters from a number of outside stations of the power supply system to a central station with only one or with only a few receivers.

On account of the large number of transmitters required in this second case, it is necessary for economical reasons to be able to produce them at low cost. In spite of this, however, they have to meet stringent technical requirements. Due to the large number of transmitters acting on the same power supply system, their transmitting power also has to be considerably lower in this case in comparison to the case of ripple control, not only for reasons of cost but also in view of the interference which may be possibly caused by the signals from these transmitters in adjacent data-transmission systems. Proposals which have heretofore been put forward in regard to similar transmitters are based for example on mains-frequency pulse-excited oscillator circuits connected to the power supply system (cf. for example Swiss Patents Nos. 404,475-and 442,505 and British Patent No. 1,148,553).

Transmitters of this type generate not only a discrete frequency, but also a relatively densely occupied spectrum of oscillations. In practical application, this makes it difficult or even impossible to simultaneously use other discrete frequencies in the same power supply system. This is a serious disadvantage, especially in cases where data emanating from numerous sources has to be transmitted.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to obviate this disadvantage.

A further object of the present invention is to provide a method and an apparatus for generating signals where essentially only a selected frequency is transmitted which bears a fixed relationship to the mains frequency.

If a power supply system is used as a channel for the transmission of signals with the frequency f as is envisaged for an advantageous application of the present invention, a relatively high noise level can be expected in the transmission channel. Experience has shown that the interfering voltages are largely harmonics of the mains frequency f Accordingly, considerable importance is attached to selecting the optimum signal frequency On account of the relatively dense interfering frequency spectrum, it is advisable to keep the band width at the receiving end as narrow as possible, for example to limit it to only just that width which is required by the character of the data to be transmitted by the signals with the frequency f It is assumed that the signals spread out in a direction opposite to the direction of energy flow in the power supply system and that the transmitting power is several times lower than in conventional ripple-control technology. In addition to limited band width and high selectivity, receivers suitable for the present purpose also have to exhibit high sensitivity because only weak signals are received.

Since neither the mains frequency f nor the interfering frequencies that are harmonics thereof are constant in time, it is particularly difficult where a constant signal frequency f is used to find a suitable signal frequency f which still shows sufficient percentage clearance from the adjacent interfering frequencies under all circumstances, i.e. even in the event of extreme deviation of the mains frequency f from its ideal level. Where the mains frequency f is non-constant, therefore, it is of great advantage to select a non-constant signal frequency f as well. It is of particular advantage always to keep this signal frequency f in a fixed relationship to the mains frequency f The percentage clearance of the signal frequency f from the adjacent interfering frequencies will thus remain intact, even in the event of fluctuations in the mains frequency f Receivers whose response frequency automatically adapts itself to a signal frequency f varying in known manner with the mains frequency f are known, cf. for example Swiss Patent Specification No. 424,968.

By pulseexcitation of an oscillating circuit tuned to the frequency f oscillations with the frequency f can be generated with simple means. However, in addition to the required signal frequency f known transmitters which function on this principle on audio frequency excitation, also generate a more or less wide spectrum of undesirable interfering frequencies.

According to the present invention, there is provided a method of generating, in a power supply system, a transmission signal with a frequency f bearing a fixed relationship to the mains frequency f of the power supply system, wherein an impulse sequence whose repetition frequency bears the aforementioned fixed relationship to the mains frequency f is formed by frequency multiplication and frequency division, and a tank or oscillating circuit connected to the power supply system and tuned at least approximately to the said repetition frequency is excited by it into oscillations in each cycle of the impulse sequence.

Accordingto the present invention, there is also provided an apparatus for generating, in a power supply system, a transmission signal with a frequency f bearing a fixed relationship to the mains frequency f of the power supply system, comprising an impulse generator, to the input of which a mains frequency control signal source is connected, the impulse generator including a frequency multiplier and a frequency divider in series with a pulse shaper, a controllable switching element the input of which is connected to the impulse generator output, and an oscillating or tank circuit connected to the power supply system and tuned at least approximately to the frequency f the tank circuit being coupled to a circuit controlled by the switching element.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. I is a simplified circuit diagram of a first embodiment of transmitter designed according to the teachings of the present invention;

FIG. 2 is a circuit diagram of a second embodiment of transmitter according to the present invention;

FIG. 3 is a circuit diagram of a third embodiment of transmitter according to the present invention;

FIG. 4 is a diagram depicting voltage characteristics of an impulse generator of the third inventive embodiment of transmitter; and

FIG. 5 is a detailed circuit diagram of a fourth embodiment of transmitter designed according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The various embodiments of transmitters described by way of example in the following are substantially free from the disadvantage of generating a wide spectrum of undesirable interfering frequencies. They are all based on the fact that energy is delivered by impulses to an oscillating or tank circuit tuned at least approximately to the frequency f at least once during each cycle of the required frequency f preferably for about one-quarter of a cycle.

Now, FIG. I is a simplified circuit diagram of a first embodiment of transmitter. An LC-oscillating or tank circuit I with an impedance coil 2 and a capacitor 3 is connected to a phase conductor P and to the neutral conductor of a power supply system with the mains voltage U and the frequency f,, The LC-oscillating circuit I is closed through the impedance of the power supply system. Accordingly, any oscillating current generated in the LC-oscillating circuit 1 flows substantially through the phase conductor p to the feed of supply point and from there back through the neutral con ductor O. A controllable switching element is coupled to the LC-oscillating circuit 1 through a winding 4 coupled to the coil 2. In the embodiment shown in FIG. 1, a switching transistor 5a serves as the controllable switching element 5. However, other known eontrollable switching elernnts, particularly from the semiconductor art, such as for example thyristors and the like, may also be used for this purpose.

The emitter 6 of the switching transistor 5a is connected through a lead 7 to a terminal 8. The collector 9 of the switching transistor 50 is connected through the coupling winding 4 and through a resistor 10 to a terminal 11. A supply voltage U is applied between the terminals 8 and II. The supply voltage U can be generated for example in known manner by a known type of supply device connected to the phase conductor P and the neutral conductor 0.

The control input of the controllable switching element 5, i.e. the base terminal or contact 12 of the switching transistor 50, is connected through a lead 13 to an output 14 of an impulse or pulse generator 15. The impulse generator 15 is connected to the terminals 11 and 8 through leads l6 and 17, respectively. One input 18 of the impulse generator 15 is connected through a lead 19 to the phase conductor P.

Details of the impulse generator 15 will be considered more fully in conjunction with FIG. 2, but at this point it is mentioned that the impulse generator 15 generates impulses whose repetition frequency is consistent with the signal frequency f to be generated. The controllable switching element 5 is controlled by these impulses. Current impulses flow through the coupling winding 4 in the supply circuit of the switching element 5 at the rhythm of the frequency f with the result that the LC-oscillating or tank circuit I is excited into forced oscillations with the frequency f The impulse frequency f,- generated by the impulse generator 15 is kept in a fixed relationship to the mains frequency f,,, by a mains frequency signal delivered through the lead I9 to the impulse generator 15 in a manner that will be described further on.

The impulses given off from the impulse generator 15 and the current impulses flowing through the coupling winding 4 preferably have an impulse pause ratio of approximately 1 3. By virtue of the coherent excitation of the LC-oscillating circuit 1, an oscillation of substantially constant amplitude and frequency is generated therein in contrast to other known pulse-excited transmitters which generate damped cycles.

A second type of transmitter will now be described by way of example with reference to FIG. 2 with particular emphasis upon the structure and mode of operation of the impulse generator 15. Identical components carry the same reference numerals as employed in FIGS. 1 and 2.

The impulse generator 15 contains a frequency multiplier 20. One example of a suitable frequency multi plier 20 is an oscillator synchronised in known manner to a harmonic of the mains frequency f The input 18 of the impulse generator 15 is connected to input 21 of the frequency multiplier 20. An output 22 of the frequency multiplier 20 is connected to an input 23 of a frequency divider 24. An output 25 of the frequency divider 24 is connected to the input 26 of a pulse shaper 27 whose output 28 is connected to the output 14 of the impulse generator 15. As already described with reference to FIG. I, the output 14 of the impulse generator 15 is connected to the input of the controllable switching element 5.

The frequency multiplier 20 can also be in the form of, for example, a multivibrator which oscillates at a frequency ntimes higher than a control frequency f delivered to it. Accordingly, the output frequency of the frequency multiplier 20 is n f This frequency is delivered to the frequency divider 24 which is adjusted to a dividing ratio of l :p. The output frequency of the frequency divider is thus (n 'f )/p =f equal to the required signal frequency.

A following pulse shaper 27, for example a monostable multivibrator or monoflop, generates an impulse pause ratio of for example I 3 which is of advantage insofar as excitation of the tank circuit is concerned. The impulses arriving with the repetition frequency f; at the output 14 of the impulse generator 15 then drive the controllable switching element 5 in each cycle of an oscillation with the frequency f so as to be conductive for one-quarter of a cycle, so that the LC-oscillating circuit 1 is coherently excited with f by the current surges flowing through the coupling winding 4 and the controllable switching element 5 in its supply circuit.

If the signal frequency f is intended to amount to 275 c/s (ideal value) for a mains frequency of 50 c/s (ideal value), the frequency multiplier can be adjusted to a factor (n) of II and the frequency divider 24 to a quotient (p) 2 for this case. The signal frequency f is thus always equal to 5.5 times the mains frequency f,,,, even in the event of fluctuations in the mains frequency. As can readily be seen, other fixed ratios between the signal frequency f and the mains frequency fcan be adjusted by altering the aforementioned factor or quotient. I

A third emboidment of transmitter shown by way of example in FIGS. 3 and 4 illustrates how an impulse sequence with the aforementioned impulse pause ratio of l 3 can be readily generatedat the output 14 of the impulse generator 15, even in the event of fluctuating frequency. In each of FIGS. 1, 2 and 3, identical components carry the same reference numerals.

Both the frequency multiplier 20 and also the frequency divider 24 are constructed in known manner in such a way that their output signals U and U respectively, follow a rectangular pattern as a function of time as shown in FIG. 4 in graphs a and b.

If, according to FIG. 3, the output signal U (cf. FIG. 4, graph a) of the frequency multiplier 20 is delivered through a lead 29 to a first input 30 of an AND-gate 31, and the output voltage U (cf. FIG. 4, graph b) of the frequency divider 24 through a lead 32 to a second input 33 of this AND-gate 31, the output voltage U at the output 34 of the AND-gate 31 follows a time pattern of the type shown in graph 0, FIG. 4. Since the output signal U already has the required frequency f the impulses of the output voltage U also occur with the repetition frequency f By virtue of the aforementioned logical configuration of the two voltages U and U the output signal U receives the required impulse pause ratio of l 3, even where the mains frequency f and hence the frequency f is subjected to fluctuations. The output voltage U of the AND-gate 31 is delivered through a lead 35 to the output 14 of the impulse generator 15 and through the lead 13 to the input 12 of the controllable switching element 5.

A fourth embodiment of transmitter will now be described by way of example with reference to FIG. 5. In FIG. 5 identical components also carry the same reference numerals as in FIGS. 1, 2 and 3.

A mainsfrequency control signal is delivered through the lead 19 from the phase conductor P to the input'l8 of the impulse generator 15 by way of resistor 36. This control signal is delivered through the resistor 36 to the base terminal 37 of a transistor 38. A diode 39 is connected between the base terminal 37 and the lead 7 which is at zero potential. This diode 39 limits the negative voltage occurring at the base of the transistor 38. The transistor 38 is driven to be fully conductive by the positive half waves of the mains frequency control signal in such a way that output signals of opposite phase occur at its emitter terminal 40 through an emitter resistance 41 and at its collector terminal 42 through a collector resistance 43. These output voltages have a substantially rectangular waveshape or pattern. Accordingly, corresponding flanks in the two output signals are always directed opposite to one another.

The output signals occurring at the transistor 38 are differentiated through an RC-section or circuit embodying a capacitor 44 and a resistor 45 and through another RC-section with a capacitor 46 and a resistor 47. These differentiated output signals are delivered in known manner as control signal to a conventional multivibrator 52 from the circuit terminal or junction 48 or 49 through a diode 50 or 51 respectively. The sweep frequency of the multivibrator 52 is synchronised, which moreover is dimensioned in such a way that it oscillates at n-times the mains frequency f The factor n of the frequency multiplier 52 and the quotient of the frequency divider are best selected in such a way that a signal frequency f, which no longer coincides with a harmonic of the mains frequency f is generated. This is the case where n/p does not amount to a whole number. A signal with the frequency n -foccurs at an output 22 of the multivibrator 52 acting as the frequency multiplier 20. In the present embodiment according to FIG. 5, the frequency divider 24 (cf. FIG. 3) is in the form of commercially available module SN 7472, a product of Texas Instrument Corporation, USA.

As already mentioned with reference to FIGS. 3 and 4, the output signal U of the frequency multiplier 20 (in this case realized by the multivibrator 52) and the output signal U of the frequency divider 24 (module SN 7472) are in a logical configuration. The diodes 53 and 54 and 55 connected to the terminal 11 through a resistor 56 are used for this purpose. The diode 55 is further connected through a resistor 57 to the output 14 of the impulse generator 15 which, in addition, is connected to the lead 7 via a resistor 58. This logical configuration circuit also acts as a pulse shaper as previously considered.

It can be seen from the fourth embodiment of transmitter shown in FIG. 5 that a transmitter according to the invention can be obtained with very little outlay, especially where integrated circuits are used. The need for the rigid ratio between the signal frequency f abd the mains frequency f which has to be satisfied at the transmitting end is ideally fulfilled.

At the receiving end, the need for consistency between the receiver response frequency and the signal frequency f governed by the mains frequency f can be fulfilled with simple means, as already mentioned.

The present invention is used with particular advantage for example where it is desired to report the position of switching element in a power distributing system to a central station by transmitting signals through the power supply system. It is possible with a transmitting power of only a few watts to reliably cover distances of for example 10 kilometers and more.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,

What is claimed is:

l. A method of generating in a power supply system a transmission signal for remote control purposes with a frequency bearing a fixed relationship to the mains frequency of the power supply system, comprising the steps of forming by frequency multiplication and frequency division an impulse sequence whose repetition frequency bears said fixed relationship to the mains frequency. and exciting into oscillation by means of the repetition frequency during each cycle of the impulse sequence a tank circuit connected to the power of supply system and tuned at least approximately to the rep etition frequency, said tank circuit only being excited into forced oscillation in the presence of the repetition frequency.

2. The method as defined in claim 1, including the step of only exciting into oscillation the tank circuit once during each cycle of the transmission signal frequency to be generated.

3. The method as defined in claim 1, including the step of exciting into oscillation the tank circuit during each cycle of the transmission signal frequency to be generated for approximately one-quarter of the cycle thereof.

4. The method as defined in claim 1, including the step of obtaining the impulse sequence whose repetition frequency is equal to the required transmission signal frequency by logical coupling of a signal obtained by frequency multiplication and a signal obtained by frequency division.

5. The method as defined in claim 1, including the step of selecting the impulse sequence frequency so as not to coincide with a harmonic of the mains frequency.

6. An apparatus for generating in a power supply system a transmission signal for remote control purposes with a frequency bearing a fixed relationship to the mains frequency of the power supply system, comprising an impulse generator having an input and an output, a mains frequency control signal source connected with the input of said impulse generator, said impulse generator including a frequency multiplier and a frequency divider in series with a pulse shaper, a controllable switching element having an input connected with the output of said impulse generator, and a tank circuit connected to the power supply system and tuned at least approximately to the transmission signal frequency, said tank circuit being coupled with a circuit controlled by the controllable switching element and delivering the generated oscillating current into the power supply system 7. The apparatus as defined in claim 6, wherein said frequency multiplier embodies an oscillator synchro nized to a harmonic of the mains frequency.

8. The apparatus as defined in claim 7, wherein the oscillator comprises a multivibrator synchronized by a mains frequency control signal to a harmonic of the mains frequency.

9. The apparatus as defined in claim 6, wherein said pulse shaper comprises a monostable multivihrator.

10. The apparatus as defined in claim 6;, further including a logical switching element having a pair of inputs and an output, one input of said logical switching element being connected to the output of the frequency multiplier, the other input of said logical switching element being connected to the output of the frequency divider, and the output of said logical switching element being connected to the input of the controllable switching element. 

1. A method of generating in a power supply system a transmission signal for remote control purposes with a frequency bearing a fixed relationship to the mains frequency of the power supply system, comprising the steps of forming by frequency multiplication and frequency division an impulse sequence whose repetition frequency bears said fixed relationship to the mains frequency, and exciting into oscillation by means of the repetition frequency during each cycle of the impulse sequence a tank circuit connected to the power of supply system and tuned at least approximately to the repetition frequency, said tank circuit only being excited into forced oscillation in the presence of the repetition frequency.
 2. The method as defined in claim 1, including the step of only exciting into oscillation the tank circuit once during each cycle of the transmission signal frequency to be generated.
 3. The method as defined in claim 1, including the step of exciting into oscillation the tank circuit during each cycle of the transmission signal frequency to be generated for approximately one-quarter of the cycle thereof.
 4. The method as defined in claim 1, including the step of obtaining the impulse sequence whose repetition frequency is equal to the required transmission signal frequency by logical coupling of a signal obtained by frequency multiplication and a signal obtained by frequency diviSion.
 5. The method as defined in claim 1, including the step of selecting the impulse sequence frequency so as not to coincide with a harmonic of the mains frequency.
 6. An apparatus for generating in a power supply system a transmission signal for remote control purposes with a frequency bearing a fixed relationship to the mains frequency of the power supply system, comprising an impulse generator having an input and an output, a mains frequency control signal source connected with the input of said impulse generator, said impulse generator including a frequency multiplier and a frequency divider in series with a pulse shaper, a controllable switching element having an input connected with the output of said impulse generator, and a tank circuit connected to the power supply system and tuned at least approximately to the transmission signal frequency, said tank circuit being coupled with a circuit controlled by the controllable switching element and delivering the generated oscillating current into the power supply system.
 7. The apparatus as defined in claim 6, wherein said frequency multiplier embodies an oscillator synchronized to a harmonic of the mains frequency.
 8. The apparatus as defined in claim 7, wherein the oscillator comprises a multivibrator synchronized by a mains frequency control signal to a harmonic of the mains frequency.
 9. The apparatus as defined in claim 6, wherein said pulse shaper comprises a monostable multivibrator.
 10. The apparatus as defined in claim 6, further including a logical switching element having a pair of inputs and an output, one input of said logical switching element being connected to the output of the frequency multiplier, the other input of said logical switching element being connected to the output of the frequency divider, and the output of said logical switching element being connected to the input of the controllable switching element. 